version
Study on Multi-Users Interference in Vehicle to Vehicle Visible Light Communications
Emmanuel Plascencia
Institut VEDECOM | Laboratoire d’Ingénierie des Systèmes de Versailles University of Versailles
Emmanuel Plascencia, Oyunchimeg Shagdar, Hongyu Guan and Luc Chassagne
01/10/2020
2
Emmanuel Plascencia
He obtained his bachelor's degree in Electronic Engineering
from the Technological Institute of León, Mexico in 2016,
and a master's degree in Applied Sciences in medical
physics and instrumentation from the University of
Guanajuato, Mexico in 2018. He is a 2nd-year Ph.D.
student at the University of Versailles in codirection with
the Vedecom Institute in France. His thesis research
includes Visible Light Communication for vehicle platoons,
as well as the Physical layer (PHY) and Medium Access
Control (MAC) for VLC technology.
01/10/2020
PRESENTER'S PROFILE
3
01/10/2020
Visible Light Communications (VLC) can play an important role in the Cooperative Intelligent
Transport Systems (C-ITS) by enabling vehicles to communicate with nearby vehicles (V2V) and
infrastructure (V2I) by offering virtually unlimited and unregulated spectrum.
INTRODUCTION
01011010
01011000110
4
01/10/2020
EXISTING EFFORTS ON VLC & MOTIVATION OF THE WORK
Physical Layer (PHY)
Medium Access Control (MAC)CSMA/CA (802.15.7/r1) – Carrier sensingis challenging in VLC (directional half-duplex link)ALOHA
Manchester codingMiller codingColor shifting…
Filtering stages
Pre-equalization TxPost-equalization RxLogarithmic AmplificationsRGB arrangements…
Huge number of efforts
Very limited number of efforts
Is Multi-Users Interference (MUI) being problematic in VLC? → Do we need MAC?
Coding techniques
5
01/10/2020
MODELING IMPACT OF VLC MULTI-USERS INTERFERENCE
𝑅𝑜 𝜙 = ൞
(𝑚𝑖 + 1)
2𝜋𝐶𝑜𝑠𝑚𝑖 𝜙 𝜙 ∈ −𝜋
2𝜋2
0 𝜙 ≥ 𝜋2
Angular distribution (Tx) Photodiode area (Rx)
𝐴𝑒𝑓𝑓(𝜓) = ൝𝐴𝑟𝐶𝑜𝑠 𝜓 0 ≤ 𝜓 ≤ 𝜋
2
0 𝜓 > 𝜋2
𝐻 𝜙,𝜓 = ቐ𝐴𝑟(𝑚𝑖 + 1)
2𝜋𝑑2𝐶𝑜𝑠𝑚𝑖 𝜙 𝐶𝑜𝑠(𝜓) 0 ≤ 𝜓 ≤ 𝜓𝑐
0 𝑒𝑙𝑠𝑒𝑤ℎ𝑒𝑟𝑒
𝐻0 𝜙,𝜓 = ቐ𝐴𝑟(𝑚𝑖 + 1)𝑃𝑡
2𝜋𝐶𝑜𝑠𝑚𝑖 𝜙 𝐶𝑜𝑠(𝜓) 0 ≤ 𝜓 ≤ 𝜓𝑐
0 𝑒𝑙𝑠𝑒𝑤ℎ𝑒𝑟𝑒
VLC channel Model
The receiver power 𝑃𝑟, is hence
𝑃𝑟 = 𝐻 𝜙,𝜓 𝑃𝑡 =𝐻0 𝜙,𝜓
𝑑2
6
MUI - zone
01/10/2020
PDR = (1 − 𝐵𝐸𝑅)𝐿
Packet Delivery Ratio (PDR) depends on the Bit-Error Rate (BER) and the packet size (L). BER is afunction of Signal to Interference plus Noise Ratio (SINR).
𝐵𝐸𝑅 = 𝑄 𝑆𝐼𝑁𝑅 = 𝑄 𝑃𝑟𝑀𝑈𝐼+𝑁
SINR requirement (𝑆𝐼𝑁𝑅𝑡ℎ ∶ 𝑚𝑖𝑛𝑖𝑚𝑢𝑚 𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑑 𝑆𝐼𝑁𝑅)
𝑃𝑟𝑀𝑈𝐼 + 𝑁
≥ 𝑆𝐼𝑁𝑅𝑡ℎ
𝑃𝑖 𝑑𝑖𝑟 ≥𝑃𝑟 𝑑𝑡𝑟𝑆𝐼𝑁𝑅𝑡ℎ
− 𝑁
𝑆𝐼𝑁𝑅𝑡ℎ = 𝑄−1 1 − 𝐿 𝑃𝐷𝑅𝑟𝑒𝑞2
MODELING IMPACT OF VLC MULTI-USERS INTERFERENCE
Impact of MUI
𝑑𝑖𝑟
MUI-zone (𝑑𝑖𝑟):Simultaneous transmission from a node in the MUI-zone results in a
failure for the communication between the intended transmitter
and receiver.
Intended receiver
Intended transmitter
Interfering node
7
01/10/2020
𝑑𝑟𝑖 = 𝑑𝑡𝑟 𝑆𝐼𝑁𝑅𝑡ℎ
Relation between Tx and RX distance (𝑑𝑡𝑟) andthe MUI zone on a multi-lane (𝑙0, 𝑙1, 𝑙2, 𝑙𝑛 …)
𝑙 = 𝑑𝑖𝑟 +
𝑘=1
𝑛𝑙
𝑙𝑘 +
𝑘=1
𝑛𝑟
𝑙𝑘
The probability of finding 𝑖 vehicles in the MUI zone
𝑃 𝑖, 𝑙 =(𝛽𝑙)𝑖 𝑒−𝛽𝑙
𝑖!
Communication success probability
𝑃𝑠 =
𝑖=0
∞
𝑃(𝑖, 𝑙) 1 − 𝜏 𝑖
Where 𝜏 is the channel access probability:function of transmission time (𝑇𝑡𝑥) and messagegeneration interval (𝑇𝑖𝑛𝑡𝑒𝑟𝑣𝑎𝑙)
𝜏 =𝑇𝑡𝑥
𝑇𝑖𝑛𝑡𝑒𝑟𝑣𝑎𝑙
SUCCESS PROBABILITY WITH PRESENCE OF MUI
Impact of MUI
Road length in MUI-zone:
MUI - zone
InterferingNodeNode that does
not impact on the
communication between Tx and
Rx
8
Parameter Value
PD reference S6967 Hamamatsu
𝐴𝑒𝑓𝑓 100mm x 100mm
PD efficiency 0,5(A/W)
FoV (𝜓) 55°
PD capacitance 1,2 𝜇𝐹/𝑚2
Transmission frequency 500 KHz
Transmission power 1 Watt (Car taillight)
Transmitter Semi-angle 𝜙1
2
20°
Inter-PD separation distance 1,2 meters
Road lane width 2,5 meters
Data size (L) 1000 Bytes
01/10/2020
MATLAB parameters + Simulink Model
PERFORMANCE EVALUATION: VLC SUCCESS PROBABILITY
9
01/10/2020
Results
PERFORMANCE EVALUATION: VLC COMMUNICATION RANGE & MUI ZONE VALIDATION
VLC communication range on a 7-lanes road.MUI zone for 90% of PDR requirement. Blue and yellow zones aresimulation results, Red transparent area is the results of theanalytical model.
10
01/10/2020
Results
PERFORMANCE EVALUATION: PROBABILITY TO GET VEHICLES IN MUI-ZONE & SUCCESSFUL TRANSMISSION
PDR performances of VLC in 3-lanes highway scenario ( 𝑙 =203m).a) Low Density - maximum 1 vehicles on the roadb) Medium Density - maximum 10 vehicles on the roadc) High Density - maximum 20 vehicles on the road.
PDR performances of VLC in 7-lanes highway scenario ( 𝑙 =529m).a) Low Density - maximum 2 vehicles on the roadb) Medium Density - maximum 26 vehicles on the roadc) High Density - maximum 53 vehicles on the road.
11
01/10/2020
CONCLUSION AND FUTURE WORK
• Development of an analytical model
• Determining multi-user interference zone
• VLC success probability for Poisson distributed road traffic.
• The Simulink simulation results confirm the correctness of the analytical model on MUI zone.
• Even with low traffic densities and low message generation rates, the vehicles in the MUI zone
can significantly degrade the PDR performance of the target VLC communication
• An inherent necessity of a MAC protocol for V2V communications.
Future work:
o Improvement of the theoretical model by considering shadowing effect by bodies of vehicles.
o Conduct study on MAC that is aware of the presences of vehicles in the MUI zones.
Together to accelerate the mobility of tomorrow !
Thank you for your attention
